Regulation of direct current



1 LA VERNE R. PHILPOTT 2,146,761

REGULATION OF DIRECT CURRENT Filed Dec. 9, 1936 2 Sheets-Sheet 1 IE LE; .L L IS; E

+ w "I i I INVENTOR LaVer'ne R.Philpo ATTORNEY Feb. 14, 1939. LA VERNE PHILPOTT 2,146,761

REGULATION OF DIRECT CURRENT 2 Sheets-Sheet 2 IN V! N TOR Filed Dec. 9, 1936 Liz/Verne R Pl-uZpot/b w a, M

v ATTORNEY Patented Feb. .14, 1939 2,146,761

UNITED STATES PATENT OFFICE REGULATION OF DIRECT CURRENT u Verne a. Phllpott, Washington, D. c.

Application December 9, 1936, Serial No. 114,917

.15 Claims. (Cl. 171-312) (Granted under the act or March a, 1883, as amended April so, 1928; :10 o. c. m)

This invention relates to apparatus for and a is shown in Fig. 4 wherein the change in current method of maintaining the current constant in a is Pl ed against the change in voltage. direct current circuit regardless of changes in Fig. 2 shows a second resistance iii in series t impressed voltage with resistance R, the eflective value of the former Broadly stated, it is the object of this invention being variable at will by changing the position 5 to maintain the current constant, within very 0f the Sliding ntact II and thus the line curclose limits, in a direct current circuit wherein rent I may be held steady even though the imthe voltage varies, by automatically changing the pre d voltage change t is app t that the impedance of a network associated with such cirvolt e across resistance III will have the same 1. cult. value as between the points designated by the In t drawings: line 4! and that this voltage will be less than that Fig. 1 shows diagrammatically a very simple f s ur e 9 by a quant ty q al to t dr p thr method of maintaining a direct current at a conresistance R. If we represent the voltage of stant value; source 9 by E1. and represent time by t, the variall Fig. 2 is also diagrammatic and illustrates a tioninthe eflective value of resistance III to make 5 somewhat more complicated method of attaining the equation the result set forth; dI

Fig. 3 illustrates the use of a vacuum tube Tit whereof the impedance may be varied manually to effect regulation of the current; 18 Z 20 Fig. 4 is a graph showing the relation between voltage and current; wherein R is the value of resistance R, and R is Fig. 5 shows schematically a network embodythe value of resistance ing the principle of my invention associated with In 3 the Voltage across R is controlled by a direct current circuit; varying the impedance of a vacuum tube I2 that 25 v Fig 5 Shows graphically the relations between is connected in series with the load resistance R. the plate current the plate voltage and the grid Suitable initial values for passing the required voltage to keep the current output constant; current may be Set up by varying the bias on grid Fig. 7 is a graphic representation of the curof tube through change in the point of rent and voltage relations in anetwork embodying connection thereof to Voltage divider that is 30 the principle of my invention when the current conneeted in series with battery and also by through the regulated circuit is held at a uniform ehehgmg the current through filament of tube value I! by altering the resistance I! in the filament Fig 8 illustrates a modified embodiment of my circuit thereof and the current thereafter may be mventiom held constant by appropriate changes of grid 35 It is very necessary to keep the current through voltage- This device is manually adjusted d certain direct current apparatus at a constant does not respond automatically to hanges in value, P rticularly when such apparatus is being Voltage Source utilized to supply energy to measuring devices, 5 shows a network applying e prinsuch as t an e1eetremegnet serving as a source ciples of my invention to the automatic regulaof magnetic flux where t results would be f tion of a direct current. This network comprises no value or misleading 1f the direct current were a resistance Is, a vacuum tube 20 and a vacuum permitted t change in strength, The underlying tube 2| in parallel with each other and in series principle of my invention will first be made clear i h the load The tube 29 has s Plate 22 by reference to some very elementary cir it connected to the negative side of the load and its 45 Fig. 1 h ws a, simple resistance R of a value cathode 23 connected to the negative lead, the recontrolled by the sliding or tap contact 0 across Sistance being connected w e he plate and a source of direct voltage 9, It i evident t t the cathode of tube 20. A by-pass condenser 24 th value of 11 dependent upon t voltage of 9 is connected across the output circuit of the tube and the value of R and changes when'the value 20. Plate and cathode 25 Of tube are like- 50.

of either of these is altered. The current in this Wise respectively connected to the n a ive side circuit may be varied by changing the position of the load circuit and the negative lead, the grid of tap 8 on resistance R or the line current I may 16 f t be 2| ng nn d to Plate 44 y a be maintained constant when the voltage of source suitable oscillatory network, shown in Fig. 5, as I varies by manipulation of tap contact 8. This consisting of the variably coupled inductances 21 55 .the point about which the voltage of grid 3! will fluctuate due to voltage changes across resistance 29 caused by variations in the plate current of tube 2!. It is evident that an increase in the voltage impressed on plate M will result in a greater how of current through resistance 2 and this will have the effect of decreasing the voltage on grid 35 and thereby increase the impedance of tube 29. The constant voltage impressed on grid 3! by battery 34 is designated Ego while the variable voltage from the oscillator 2! is designated E v. L

The operation of the apparatus shown in Fig, 5 may be explained by reference to the graph of Fig. 6 wherein the current through the load resistance R is plotted along the positive ordinate, the grid voltage of tube 2% is plotted on the negative ordinate and the positive abscissa represents the plate voltage, these three quantities being represented for convenience by IR, Eg, and E13, respectively. The curve A shows the plate current of tube 2! plotted against the plate voltage with grid voltage zero. Suppose it is desired to maintain a steady direct current having value represented by a line B, it is apparent that the grid voltage must not go to zero but must have a minimum value represented by the abscissa of the point of intersection of line B with curve A and that the value of the grid voltage must progressively decrease as the plate voltage increases to prevent change in the current through the tube. The line D in Pig. in shows the value of the voltage impressed on grid 3i of tube 29 due to changes in the output current of tube 2i and the consequent variation in the voltage across resistance 2d. The line. C in Fig. 6 shows the resultant or net voltage applied to grid 35 by the connection to resistance 2% and also by the voltage divider resistance 33, the value of the steady voltage derived from battery 3% being equal to the ordinate distance between equal abscissa values on the lines C and D and is opposed to the voltage derived from oscillater 28 to shift the abscissa of the initial point of line C to the same value as the abscissa of the intersection of line B with curve A. This makes the regulation of the current independent of the load resistance R.

In Fig. 7 the curve A is the current through tube 2% plotted against the voltage across the parallel connected elements 39, 2i! and 25, that is, it is the line voltage less the drop through resistance R plotted against the current through tube 213 at zero grid bias. The lines B, C and D represent the same quantities as in Fig. 6 but, as above stated, the line E represents the efiective voltage across the parallel connection elements and the line I represents the current. Line F shows the sum of the currents through tube 2i and resistance i9 plotted against the effective voltage E and line G shows the relation between current through tube if! and the same voltage. It will be noted that the slopes of lines F and G are opposite in sense but of equal value and therefore the resultant total current is constant as represented by line B. Within the capacity range of tube 29 the current through the load resistance R is thus seen to be independent both of the line voltage range of the regulator.

arsenal and of the magnitude of the load resistance. Any ripple in the voltage on the supply line can be filtered out by making resistance 29, condenser 3b, the inductances 2i, and condenser 28 of suitable values.

The circuit of Fig. 8 is substantially the same as that in Fig. 5 except that the battery 3%, which supplies theconstant voltage to grid 3i, is replaced by a resistance 35 in parallel with a gas tube 36 and in series with a resistance 37 connected to the positive supply line, the variations in the voltage across resistance 35 being eliminated by the change in current through gas tube 36 in response to such changes. The tube 36 forms a very satisfactory substitute for battery 34% when resistances 35 and 3'! have high values.

As a specific example, the present invention was applied to regulate the current through an electromagnet having a resistance of 2200 chins, requiring 10 i milliamperes. Referring to Fig. 5, the several elements had the following values:

Resistance ill 5000 ohms.

Tube 29 Type 2A3.

Tube 2i. Type "18.

Battery 34 22 volt C battery. 2?, 28-. Set for 500 kilocycles. Condenser 2d 4 mi.

Using a meter capable of reading current at 108 milliamperes accurate to milliampere, the system was adjusted to cover a-range of input voltage from 100-118 volts at the 60 cycle supply line feeding a rectifier that directly supplied Er. without perceptible change of current. As the magnet warmed up and its resistance changed approximately 10 percent no current change could be detected when the change was in the When direct heated tubes were used, and adjustments made so that a transient in the voltage caused a more slight transient in I, While a permanent shift of voltage if sufficiently sudden would cause a slight transient in I that would disappear as soon as the filaments reached the new temperature equilibrium. When a battery or a well regulated line was used to supply the filaments of the tubes. no transients appeared in I for any cause, nor was there any permanent change in I with changing EL.

The invention herein described and claimed may be used and/or manufactured by or for the Government of the United States of America for governmental purposes withoutthe payment of any royalties thereon or therefor.

I claim;

1. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a triode having a grid, an anode, and a cathode with said anode connected to said low voltage side and said cathodeconnected to said negative lead;

.a first resistance connected between said cathode and said anode, an oscillatory network connected to said low voltage side; a vacuum tube having a grid, an anode and a cathode, the grid and the anode thereof being operatively, connected to said network and-the cathode thereof being connected to said negative lead; a capacitance and a second resistance connected in parallel between said cathode and said network, means variably connecting a point on said second resistance to the grid of said triode to apply thereto a negative bias proportional to the output current of said vacuum tube, said means including a variable resistance, and a source of potential connected across said variable resistance to apply to the grid of said triode a steady potential to set at a predetermined position the point about which said triode operates.

2. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a triode having a grid, an anode and a cathode with said anode connected to said low voltage side and' said cathode connected to said negative lead; a first resistance connected-between said cathode and said anode, an oscillatory network connected to said low voltage side; a vacuum tube having a grid, an anode and a cathode, the grid and the anode thereof being operatively connected to said network and the cathode thereof being connected to said negative lead; means to impress a constant voltage upon the grid of said triode, and means to impress upon the grid of said triode a voltage that is increasingly negative in proportion to any increase of current in the output of said vacuum tube.

3, The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a triode having a grid, an anode and a cathode with said anode connected to said low voltage side and said cathode connected to said negative lead; a first resistance connected between said cathode and said anode, an oscillatory network .connected to said low voltage side; a vacuum tube having a grid, an anode and a cathode, the grid and the anode thereof being operatively connected to said network and the cathode thereof being connected to said negative lead; means to impress a constant voltage upon the grid of said triode, and means responsive to changes in the current in said positive lead to vary the voltage on the grid of said triode to oppose such changes.

4. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a triode having a grid, an anode and a cathode with said anode connected to said low voltage side and said cathode connected to said negative lead; a first resistance connected between said cathode and said anode, an oscillatory network connected to said low voltage side; a vacuum tube having a grid, an anode and a cathode, the grid and the anode thereof being operatively connected to said network and the cathode thereof being connected to said negative'lead; means to impress, a conother; the plates and cathodes of said triode and said vacuum tube being so connected in the system that each plate is at a higher potential than is the respectively cooperating cathode, said resistance being connected between the anode and the cathode of said triode; elements constituting an oscillatory network associating the grid and the plate of said vacuum tube, a first resistance and a capacity in parallel operatively connected between the cathode of said tube and said network, means including a second resistance variably connecting a point on said first resistance to the grid of said triode to impress on the grid thereof a potential to vary the negative bias on the grid of said triode proportionately to the output current of said vacuum tube, and means associated with said second resistance to apply a constant potential to the grid of said triode.

6. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a constant impedance, a variable impedance, and a vacuum tube connected in parallel with each other and in series with said load, the plate of said tube being at higher potential than the cathode thereof; an oscillatory network connecting the grid and the plate of said tube, means to set the impedance of said variable impedance at a predetermined value, and means associated with said tube connected to vary the said im- 1 pedance to oppose changes in the current supplied to said load.

7. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a constant impedance, a variable impedance, and means constituting a third current path,.said impedances and said means being all connected in parallel with each other and in series with said load, said means being responsive to changes in current through said load and so associated with said impedance as to vary said impedance to oppose the said changes in current.

8. The combination with a device constituting a load in a direct current system, of a resistance,

a triode, and a vacuum tube connected in series being connected between the anode and the cathode of said triode; elements constituting an oscillatory network associating the grid and the plate of said vacuum tube, a first resistance and a capacity in parallel operatively connected between the cathode of said tube and said network, means including a second resistance variably connecting a point on said first resistance to the grid of said triode to impress on the grid thereof a' potential to vary the negative bias on the grid of said triode proportionately to the output current of said vacuum tube, and means associated with said second resistance to apply-a constant potential to the grid of said triode.

9. The combination with a device constituting a load inv a direct current system, of a constant impedance, a variable impedance, and a vacuum tube connected in parallel with each other and in series with said load, the plate of said tube being at higher potential than the cathode thereof; an oscillatory networkconnectlng the grid and the plate of said tube, means to set the impedance of said variable impedance at a predetermined value, and means associated with said tube connected to vary the said impedance to oppose changes in'the current supplied to said load.

10. The combination with a device constituting a load in a direct current system, of a constant impedance, a variable impedance, and means constituting a third current path, said impedances and said means being all connected in parallel with each other and in series with said load, said means being responsive to incipient changes in current through said load and so assoclated with said impedance as to vary said impedance to oppose the said changes in current.

11. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between'the low voltage side of said load and said negative lead; a triode having a grid, an anode and a cathode with said anode connected to said low voltage side and said cathode connected to said negative lead; a first resistance connected between said cathode and said anode, an oscillatory network connected to said low voltage side; a vacuum tube having a grid, an anode and a cathode, the grid and the anode thereof being, operatively connected to said network and the cathode thereof being connected to said negative lead; a capacitance and a second resistance connected in parallel between said cathode and said network, means variably connecting a point on said second resistance to the grid of said triode to' apply thereto a negative bias proportional to the output current of said vacuum tube, said means including variable resistance, a third resistance connected to said positive lead and in series with said variable resistance, and a gas tube connected in parallel with said variable resistance. v

12. The combination with the positive and negative leads of a direct current supply system and a device constituting a load for said system, of a capacitance connected between the low voltage side of said load and said negative lead; a triode having a grid, an anode and a cathode with said anode connected to said low voltage side and said cathode connected to said negative lead; a first resistance connected between said cathode and said anode, an oscillatory network connected to said low voltage side; a vacuum tube having a grid, an anode and a cathode, the grid and the anode thereof being operatively connected to said network and the cathode thereof being connected to said negative lead; a. capacitance and a second resistance connected in parallel between said cathode and said network, means variably connecting a point on said second resistance to the grid of said triode to apply thereto a negative bias proportional to the output current of said vacuum tube, said means including variable amaver resistance, and a device deriving current from. I said positive lead connected across said variable resistance to apply to the grid of said triode a steady potential to shift to a predetermined pcsi= tion the point about which said triode operates.

13. The combination with a device constitutinga load in a direct current system, of a resistance, a triode, and a vacuum tube connected in series with said load and in parallel with each other; the plates and cathodes of said triode and said vacuum tube being so connected in the system that each plate is at a higher potential than is the respectively cooperating cathode, said resistance being connected between the grid and the oathode of said triode, elements constituting an oscillatory network associating the grid and the plate of said vacuum tube, a first resistance and a capacity in parallel operatively connected between the cathode of said tube and said network, means including a second resistance variably connecting a point on said first resistance to the grid of said triode to impress on the grid thereof a potential to vary-the negative bias on the grid of said triode proportionately to the output current of said vacuum tube, and means associ ated with said second resistance to apply a constant potential to the grid of said triode, said means including a resistance connected to the positive lead of said system and in series with said second resistance and also including a gas tube connected in parallel with said second resistance.

14. The combination with a device constituting a load in a direct current system, of a constant impedance, a variable impedance, and a vacuum tube connected in parallel with each other and in series with said load, the plate of said tube being at higher potential than the cathode thereof; an oscillatory network connecting the grid and the plate of said tube, current carrying means deriving current from the positive lead of said system operatively associated with the said variable 1m pedance to set the impedance thereof at a predetermined value, and means associated with said tube operatively connected to vary the impedance of said variable impedance to oppose changes in current supplied to said load.

15. The combination with a device constituting a load in a direct current system, of a constant impedance, a variable impedance, and a second impedance whereof the value automatically varies in response to changes in the voltage impressed thereon, all said impedances being connected in parallel with each other and in series with said load, the current through said second impedance rising or falling in conformity with rise or fall of the voltage impressed thereon, current carrying means deriving current from said second impedance to vary the impedance of said variable impedance to oppose changes in the current applied to said load, and means to set the impedance of said variable impedance at a predetermined value.

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